Amount to Words Converter (C#/C Sharp)

Simple code to convert a number or amount from 0 to 999,999. This was originally written in VB6(by me) but since I've been trying to learn C# lately I ported this to C# as my basic exercise. I know it's just a simple code but I'm still posting this, it might useful to someone. Here's the code:

using Microsoft.VisualBasic;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;

namespace CodeMonkey
{

class AmountToWords
{
    static void Main()
 {
  Console.WriteLine("Enter amount: ");
  string amnt = Console.ReadLine();
  Console.WriteLine("{0} = {1}", amnt, NumToText(amnt));
  Console.ReadKey();
 }

 static string Ones(string strNum)
 {
  string tmp = "";
  switch (strNum) {
   case "1":
    tmp = "One";
    break;
   case "2":
    tmp = "Two";
    break;
   case "3":
    tmp = "Three";
    break;
   case "4":
    tmp = "Four";
    break;
   case "5":
    tmp = "Five";
    break;
   case "6":
    tmp = "Six";
    break;
   case "7":
    tmp = "Seven";
    break;
   case "8":
    tmp = "Eight";
    break;
   case "9":
    tmp = "Nine";
    break;
   default:
    tmp = "";
    break;
  }
  return tmp;
 }

 static string Tens(string strNum)
 {
  string tmp = "";
  string tst = Convert.ToInt32(strNum).ToString();
  switch (tst) {
   case "10":
    tmp = "Ten";
    break;
   case "11":
    tmp = "Eleven";
    break;
   case "12":
    tmp = "Twelve";
    break;
   case "13":
    tmp = "Thirteen";
    break;
   case "14":
    tmp = "Fourteen";
    break;
   case "15":
    tmp = "Fifteen";
    break;
   case "16":
    tmp = "Sixteen";
    break;
   case "17":
    tmp = "Seventeen";
    break;
   case "18":
    tmp = "Eighteen";
    break;
   case "19":
    tmp = "Nineteen";
    break;
   default:
    tmp = Ones(Convert.ToInt32(strNum).ToString());
    break;
  }

  return tmp;
 }

 static string Ties(string strNum)
 {
  string tmp = "";
  string tst = Convert.ToInt32(strNum.Substring(0, 1)).ToString();
  switch (tst) {
   case "2":
    tmp = "Twenty";
    break;
   case "3":
    tmp = "Thirty";
    break;
   case "4":
    tmp = "Forty";
    break;
   case "5":
    tmp = "Fifty";
    break;
   case "6":
    tmp = "Sixty";
    break;
   case "7":
    tmp = "Seventy";
    break;
   case "8":
    tmp = "Eighty";
    break;
   case "9":
    tmp = "Ninety";
    break;
   default:
    tmp = Ones(Convert.ToInt32(strNum).ToString());
    break;
  }

  tmp = tmp + " " + Ones(strNum.Substring(1, 1));

  return tmp;
 }

 static string Hundreds(string strNum)
 {
  string tmp = "";
  if (strNum.Length == 0)
   tmp = "";
  int ln = strNum.Length;

  if (ln == 3) {
   tmp = Ones(Convert.ToString(strNum[0])) + " Hundred ";
   int twos = Convert.ToInt32(strNum.Substring(1, 2));
   if (twos > 19) {
    tmp = tmp + Ties(Convert.ToString(twos));
   } else {
    tmp = tmp + Tens(Convert.ToString(twos));
   }
  } else if (ln == 2) {
   if (Convert.ToInt32(strNum) > 19) {
    tmp = Ties(strNum);
   } else {
    tmp = Tens(strNum);
   }
  } else {
   tmp = Ones(strNum);
  }

  return tmp;
 }

 static string NumToText(string strNum)
 {
  string tmp = "";
  int iLen = 0;
  string sCents = null;
  string sCentsText = "";
  bool isCent = false;
  string _tens = null;

  strNum = strNum.Replace(",","");

  if (strNum.Contains(".")) {
   string[] spl = CustomSplit(strNum);
   sCents = spl[1];
   strNum = spl[0];
   iLen = strNum.Length;
   isCent = true;
   if (Convert.ToInt32(sCents) > 19) {
    sCentsText = Ties(sCents);
   } else {
    sCentsText = Tens(sCents);
   }
  } else {
   iLen = strNum.Length;
   strNum = Convert.ToInt32(strNum).ToString();
  }

  switch (iLen) {
   case 1:
    tmp = Ones(strNum);
    break;
   case 2:

    if (Convert.ToInt32(strNum) > 19) {
     _tens = Ties(Convert.ToInt32(strNum).ToString("D"));
    } else {
     _tens = Tens(Convert.ToInt32(strNum).ToString("D"));
    }

    tmp = _tens + " Pesos";

    if (isCent) {
     tmp = tmp + " And " + sCentsText + " Cents";
    }
    break;
   case 3:
    tmp = Hundreds(Convert.ToInt32(strNum).ToString("D")) + " Pesos";

    if (isCent) {
     tmp = tmp + " And " + sCentsText + " Cents";
    }
    break;
   case 4:
    tmp = Ones(Convert.ToInt32(strNum.Substring(0, 1)).ToString("D")) + " Thousand " + Hundreds(Convert.ToInt32(strNum.Substring(1, 3)).ToString("D")) + " Pesos";

    if (isCent) {
     tmp = tmp + " And " + sCentsText + " Cents";
    }
    break;
   case 5:

    if (Convert.ToInt32(strNum.Substring(0, 2)) > 19) {
     _tens = Ties(Convert.ToInt32(strNum.Substring(0, 2)).ToString("D"));
    } else {
     _tens = Tens(Convert.ToInt32(strNum.Substring(0, 2)).ToString("D"));
    }

    tmp = _tens + " Thousand " + Hundreds(Convert.ToInt32(strNum.Substring(2, 3)).ToString("D")) + " Pesos";

    if (isCent) {
     tmp = tmp + " And " + sCentsText + " Cents";
    }
    break;
   case 6:
    tmp = Hundreds(Convert.ToInt32(strNum.Substring(0, 3)).ToString("D")) + " Thousand " + Hundreds(Convert.ToInt32(strNum.Substring(2, 3)).ToString("D")) + " Pesos";

    if (isCent) {
     tmp = tmp + " And " + sCentsText + " Cents";
    }
    break;
  }

  return tmp;
 }

 static string[] CustomSplit(string str)
 {
  int pos = str.IndexOf(".");
  string[] tmp = new string[3];
  tmp[0] = str.Substring(0, pos);
  tmp[1] = str.Substring(pos + 1, str.Length - (tmp[0].Length + 1));
  return tmp;
 }

    }
}

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